Melanoma is the most fatal form of skin cancer and the most common lethal skin cancer, with an estimated mortality rate of 14%. The incidence of melanoma in the United States is 60,000 new cases each year, increasing 2% per year.
Melanomas are thought to originate (in situ melanoma) in the epidermis near the dermal-epidermal junction (DEJ), causing disarray/breakdown, and progress in lateral and then vertical (invasive melanoma) growth phases leading to metastasis and death. The current methods of treating melanoma (standard surgical excisions, chemotherapy, radiation therapy, and immunotherapy) offer various degrees of success.
The National Cancer Institute estimates the overall five-year survival rate for melanoma to be 90.5%, with percentages ranging from 97.6% (localized stage I-II) to 16.2% (stage IV). Because of the tendency for melanoma to metastasize, detection of in situ melanoma is critical for efficient excision.
Electrical-Optical Sciences has developed a non-invasive and objective computer vision system intended to aid in the early detection of melanoma called MelaFind®. MelaFind® acquires and displays multi-spectral (from blue to near infrared) digital images of pigmented skin lesions and uses automatic image analysis and statistical pattern recognition to help identify lesions to be considered for biopsy to rule out melanoma. MelaFind® acquires 7 images in the visible spectral bands and 3 images in the near-infrared spectral bands. All images are analyzed for the following: (1) calibration to determine the fraction of the incident radiation that is reflected for every pixel in the image; (2) image quality control that determines whether the images are suitable for further analysis (e.g., a lesion covered with too much hair is automatically rejected and the operator is asked to clip the hair and retake the image); (3) segmentation to create a lesion mask; (4) computation of lesion properties in different spectral bands; and (5) lesion classification. The overall lesion classifier consists of 6 constrained linear classifiers, each trained to differentiate melanomas with 100% sensitivity from a particular type of lesion (low-grade dysplastic nevus, congenital nevus, common nevus, seborrheic keratosis, solar lentigo, and pigmented basal cell carcinoma). Thus, each lesion is characterized by 6 scores. A lesion is recommended for biopsy to rule out melanoma only if all scores are above the threshold value. But, because MelaFind® uses diffuse light, it can only image macroscopic structural details.
Clinical polarized dermoscopy slightly improves spatial resolution to about 100 micrometers by optically separating superficial and deeply penetrating light. This scale is sufficient for gross morphology such as pigmented networks but insufficient to detect important cellular features such as the presence of pagetoid melanocytes (PMs) and subcellular features such as branching dendritic arbores associated with melanoma.